HOUSTON (AP) — Records show that employees at a Houston-area pesticide plant where a poisonous gas killed four workers in November may have been exposed to dangerous fumes for years.

The Houston Chronicle (http://bit.ly/1DCumOm ) obtained reports with the Texas Commission on Environmental Quality about the La Porte plant owned by chemical manufacturer DuPont.

Four of the company's workers died last year after being exposed to leaking methyl mercaptan, which is used to manufacture insecticide and fungicide.

The newspaper found the company reported malfunctions with an exhaust and ventilation system inside the plant during maintenance activities for the last six years, and that it appears no one alerted officials with the Occupational Health and Safety Administration about that.

DuPont has declined to comment. Federal officials and the state agency are investigating the deaths.

More From WIBX 950